When Tolkien wrote The Lord of the Rings he intended it be just one volume. But because the price of paper was so high in the 50's when it was published, no one would have been able to afford it if it had been one volume. So it was split into three volumes: The Fellowship of the Ring,The Two Towers, and The Return of the King. Some people may argue that this makes it a trilogy not a book, but I stand with the author.